The liquor volume is a good indicator of fetal wellbeing and growth-retardation.

The vertical diameter of 8 cm and 1 cm of any liquor pocket have been used to denote polyhydramnios and oligohydramnios. The perinatal mortality has been reported to be exceed 150/1000 livebirths in diameters <1cm.

More recently the Amniotic fluid index (AFI) is replacing the vertical diameter in the documenting liquor volume. The four- quadrant technique is used.

In this technique the transducer should be perpendicular to the floor. The sum of the largest vertical pockets in the 4 quadrants is normally 13 + 5cm*.
24 cm is used (+2sd) as the lower limit of normal for the diagnosis of polyhydramnios. This produced better correlation with fetal outcome than using a single pocket of 8 cm.
A value below 5 cm is used to diagnose significant oligohydramnios after 16 weeks.